The proteins present in milk, colostrum, whey, and other such compositions produced from lactating animals, are of great value. They have unique nutritional and functional properties and are often used as ingredients in processed and prepared foods, as well as nutritional supplements and even pharmaceutical formulations. These proteins are generally categorized into two classes. The first class is a heterogenous mixture called casein and represents approximately 80% of the proteins found in milk compositions. The second class is a heterogenous mixture called whey proteins comprising the remaining 20% of the proteins in milk.
Human milk and bovine colostrum contain many bioactive whey proteins, such as lactoferrin (Lf), lactoperoxidase (Lp), immunoglobulins (Ig) and several growth factors. Bovine milk also contains these bioactive components, but at much lower levels than human milk and bovine colostrum.
Large amount of research have been carried out in studying the biological properties of these bioactive proteins from milk and whey. Harper (2000) has reviewed extensively research on many aspects of the potential benefits of these proteins. These bioactive proteins have been shown to possess many biological activities. For example, bioactive proteins from milk and whey such as immunoglobulins, lactoferrin, and lactoperoxidase, all have various types of anti-microbial activities. Bioactive proteins from milk and whey such as lactoferrin, transforming growth factor-β (TGF-β), and immunoglobulins have immune-modulation or immune enhancing effects. Bioactive proteins such as growth factors in whey have been shown to stimulate growth of tissue and cultured cells. There is increasing evidence that some bioactive proteins from milk and whey may have therapeutic value in the treatment of different types of cancer.
Researchers have employed techniques involving various types of chromatography to extract or purify the bioactive proteins from milk. For example, Morrison et al. (1963), Johansson (1969), Law and Reiter (1977) and Elliot et al. (1984) describe ways to extract lactoferrin or lactoperoxidase from various milk sources using cation exchange chromatography. Jin et al. (1991) and Francis et al. (1995) describe methods to extract growth factors from milk or whey using cation-exchange chromatography as the major step.
There are many patents related to extraction, purification, or enrichment of bioactive proteins from milk. For instance, Peyrouset et al. (U.S. Pat. No. 4,436,658) describe a process employing a weakly cation-exchange medium to isolate lactoferrin, lactoperoxidase, and immunoglobulins from whey. Okonogi et al. (U.S. Pat. No. 4,791,193) describe a process, also using cation-exchange medium, to produce high purity lactoferrin from skim milk or whey. Uchida et al. (U.S. Pat. No. 5,516,675) isolated lactoperoxidase, secretory component and lactoferrin from skim milk or whey using a cation-exchange resin. Ballard et al. (U.S. Pat. Nos. 5,866,418, 6,447,808) and Read et al. (U.S. Pat. No. 6,183,784) describe various pharmaceutical uses of milk extracts with high levels of growth factors or growth promoting activities made by cation-exchange chromatography of milk or whey. Kivits et al. (WO 01/25276) describe extracting transforming growth factor-β (TGF-β), insulin-like growth factor (IGF-1), lactoperoxidase and immunoglobulins from skim milk or whey using cation-exchange chromatography and then separating them by a hydroxyapatite column. Maubois (WO 03/006500) describe a process to enrich TGF-β, which process involves first treating milk serum protein solution at pH4-5.5 and 55-68° C. and then microfiltering the treated solution to obtain a TGF-β enriched retentate.
All of the above processes start with milk, whey, a combination or fraction thereof, and employ costly chromatographic or membrane processes to concentrate and/or purify bioactive proteins. The high cost of isolation and purification of these bioactive proteins hinders their commercial utilization. As can be seen, a need exists in the art for simple processes for isolating bioactive proteins from milk components.